1. Field of the Invention
Space-erected inflatable structures, such as reflectors, antennae, sunshields, solar sails and other structures having low weight, low packing volume and simplicity are disclosed which can be inflated in space and rigidized or used as non-rigid structures after inflation. One of the biggest disadvantages of inflatable structures is in the anisotropic nature of the flexible materials in general of which such structures are composed. This results in extreme difficulty in designing and fabricating inflatable structures to very precise shapes. The subject invention overcomes this disadvantage by providing an inflatable structure such as an inflatable space frame which can be provided with a positioning feedback system that allows the inflatable to reshape itself to a precise point and shape.
2. Description of the Related Art
Inflatable (or collapsible) antennas are described in various prior publications, such as U.S. Pat. No. 2,977,596 which recognized that due to the weight of ice forming on the structure, or to wind or other forces, the inflated structure was subject to distortion. By making the inflatable structure stronger to withstand such forces, it tended to deform due to its own weight
Another use of inflatable structures is described in U.S. Pat. No. 3,184,742, as passive repeaters in communication systems. A discussion of the problem of periodic changes in shape of the inflatable versus the significant and rather deleterious variations in strength of radio signals received from a remote transmitter by way of reflection from the inflatable is discussed.
U.S. Pat. No. 3,286,267 discloses the use of an inflatable membrane to hold an antenna subreflector in front of a main reflector as a Cassegrainan antenna which, in any antenna elevational angle other than vertical, acts as a cantilevered beam and tends to distort (arc) as a result of the transverse load applied to it by the subreflector.
Other antenna systems are disclosed in U.S. Pat. Nos. 5,047,788; 5,162,811; and 5,200,758 which employ a control system, usually of light-emitting devices mounted at locations on the antenna, to detect or locate the position of the antenna from a desired configuration or reference.
Still further, U.S. Pat. No. 5,345,238 teaches an inflatable satellite signal suppression shield which is subsequently hardened in its inflated condition.
None of the foregoing patents (the disclosures of which are incorporated in their entireties, by reference) teach an inflatable structure which consists of the following subsystems:
1.) Inflatable Structure
2.) Inflation Or Mechanical System To Alter Its Shape
3.) Position Sensing And Feedback Control System
to control the shape and positioning of the inflatable during erection and hold it in position after erection is completed.